ACOUSTIC EMISSION DETECTION OF DAMAGE EVOLUTION IN SHORT-FIBER COMPOSITES

摘要

Glass-fiber reinforced, polymer composites fabricated by pressure injection are characterized by acoustic emission (AE). Tested materials are composed of three layers with distinctly different orientation of the reinforcing phase, fabricated from 66 polyamide reinforced with 30% short fiber. The deformation processes in this type of laminate are difficult to identify because of the confined fiber orientation. Tests were made on specimens with three orientations relative to the direction of injection. By pattern recognition analysis of the AE signals recorded in monotonic tensile loading, five patterns typical of the material were identified. We used Vallen VisualClass program. The signal classes were considered in terms of various mechanisms of failure. In the analysis, the results of metallographic examinations of fiber orientation and of the condition of unloaded structure were used, as well as fracture surface examinations. The output of the analysis suggests correlations to possible failure mechanisms in the deformation process.